Don't add it as a child then... The setOrientation()-method works on the local rotation matrix of the object. It can't take the rotation of it's parents into account. What's the reason why you want to make this object a child of some other?

In that case, you might want to ad your parent/child relation by hand in your own code. The way the engine does it, the complete transformations of the parent will be executed on the child. This doesn't seem to be what you want.